#include<iostream>
#include<vector>
using namespace std;

class Solution {
public:
    int findPeakElement(vector<int>& arr)
    {
        int n = arr.size();
        int left = 0, right = n - 1;
        while (left < right)
        {
            int mid = (right - left) / 2 + left;
            if (arr[mid] > arr[mid + 1])
                right = mid;
            else if (arr[mid] < arr[mid + 1])
                left = mid + 1;
        }
        return left;
    }
};